Download or read book Widely Tunable and High Power Mid Infrared Quantum Cascade Lasers written by and published by . This book was released on 2001 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Single mode cw and pulsed distributed feedback (DFB) QC lasers with wide current tuning and high single mode power, have been realized at lambda app. = 4.6 nm; 5.2 nm, 8 nm and 9.5-10 nm and their trace gas sensing ability (parts per billion in volume or less) has been demonstrated by a variety of spectroscopic techniques. These devices, free-running and stabilized, had cw linewidths of 1 MHz and 10 KHz, respectively. Optical powers in excess of 0.5W (1W) at 300K (200K) was obtained in 75-stage structures; the cw operating temperature was increased to 175K using epitaxial-side heat sinking. New chirped superlattice active region designs yielded greater optical power per stage and allowed extension of the operating wavelength to 19 nm. These longwavelength QCLs use metal semiconductor waveguides supporting a surface plasmon mode, which allows greater optical confinement, and hence lower thresholds than conventional semiconductor waveguides of nearly double thickness. A QCL lasing simultaneously at two or more widely spaced wavelengths and a bidirectional QCL emitting different wavelengths for opposite bias polanty were demonstrated. Gain switching and active modelocking of QC lasers at 5 and 8 nm gave pulse widths of 90 ps and a few ps, respectively.

Download or read book Nonlinear Photonics in Mid infrared Quantum Cascade Lasers written by Louise Jumpertz and published by Springer. This book was released on 2017-08-31 with total page 152 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis presents the first comprehensive analysis of quantum cascade laser nonlinear dynamics and includes the first observation of a temporal chaotic behavior in quantum cascade lasers. It also provides the first analysis of optical instabilities in the mid-infrared range. Mid-infrared quantum cascade lasers are unipolar semiconductor lasers, which have become widely used in applications such as gas spectroscopy, free-space communications or optical countermeasures. Applying external perturbations such as optical feedback or optical injection leads to a strong modification of the quantum cascade laser properties. Optical feedback impacts the static properties of mid-infrared Fabry–Perot and distributed feedback quantum cascade lasers, inducing power increase; threshold reduction; modification of the optical spectrum, which can become either single- or multimode; and enhanced beam quality in broad-area transverse multimode lasers. It also leads to a different dynamical behavior, and a quantum cascade laser subject to optical feedback can oscillate periodically or even become chaotic. A quantum cascade laser under external control could therefore be a source with enhanced properties for the usual mid-infrared applications, but could also address new applications such as tunable photonic oscillators, extreme events generators, chaotic Light Detection and Ranging (LIDAR), chaos-based secured communications or unpredictable countermeasures.

Download or read book Mid Infrared and Terahertz Quantum Cascade Lasers written by Dan Botez and published by Cambridge University Press. This book was released on 2023-09-14 with total page 552 pages. Available in PDF, EPUB and Kindle. Book excerpt: Learn how the rapidly expanding area of mid-infrared and terahertz photonics has been revolutionized in this comprehensive overview. State-of-the-art practical applications are supported by real-life examples and expert guidance. Also featuring fundamental theory enabling you to improve performance of both existing and future devices.

Download or read book Solid State Mid Infrared Laser Sources written by Irina T. Sorokina and published by Springer Science & Business Media. This book was released on 2003-09-04 with total page 600 pages. Available in PDF, EPUB and Kindle. Book excerpt: This collection of authoritative reviews by leading experts provides a broad and instructive introduction to the most advanced techniques for generating coherent light in the mid-infrared region of the spectrum. With a wealth of up-to-date references – also available online.

Download or read book Widely Tunable and SI traceable Frequency comb stabilised Mid infrared Quantum Cascade Laser written by Dang Bao An Tran and published by . This book was released on 2019 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The thesis consists in developing a high-resolution mid-infrared spectrometer traceable to primary frequency standards and providing a unique combination of resolution, tunability, detection sensitivity and frequency control. A quantum cascade laser (QCL) emitting at 10.3 μm is phase locked to an optical frequency comb stabilized to a remote 1.55 μm ultra-stable reference developed at LNE-SYRTE, monitored against primary frequency standards and transferred to LPL via an active noise compensated fibre link. This results in a 0.1 Hz QCL linewidth, a stability below 10−15 at 1 s and an uncertainty on its absolute frequency below 4 × 10−14. Moreover, the setup allows the QCL to be widely scanned over 1.4 GHz while maintaining the highest stabilities and precision. This QCL was used to carry out saturated absorption spectroscopy of several molecules in a compact multipass cell. We demonstrated statistical uncertaintyon line-center frequencies at the kHz level and sub-10 kHz systematic uncertainty. We have recorded several singular K-doublets and many rovibrational transitions of methanol, in particular weak transitions and weak doublets - unreported so far. Precise parameters modelling trioxaneh ave been determined with only a few tens of rovibrational transitions recorded at unprecedented accuracy. The quadrupole hyperfine structure of an ammonia transition has been resolved for thefirst time. This setup constitutes a key element for the project aiming at the first observation of parity violation in molecules currently held at LPL, and, more generally, for various fields of physics, from atmospheric and interstellar physics to fundamental physics beyond the standard model.

Download or read book Mid infrared Quantum Cascade Lasers for Chaos Secure Communications written by Olivier Spitz and published by Springer Nature. This book was released on 2021-05-15 with total page 179 pages. Available in PDF, EPUB and Kindle. Book excerpt: The mid-infrared domain is a promising optical domain because it holds two transparency atmospheric windows, as well as the fingerprint of many chemical compounds. Quantum cascade lasers (QCLs) are one of the available sources in this domain and have already been proven useful for spectroscopic applications and free-space communications. This thesis demonstrates how to implement a private free-space communication relying on mid-infrared optical chaos and this requires an accurate cartography of non-linear phenomena in quantum cascade lasers. This private transmission is made possible by the chaos synchronization of two twin QCLs. Chaos in QCLs can be generated under optical injection or external optical feedback. Depending on the parameters of the optical feedback, QCLs can exhibit several non-linear phenomena in addition to chaos. Similarities exist between QCLs and laser diodes when the chaotic dropouts are synchronized with an external modulation, and this effect is known as the entrainment phenomenon. With a cross-polarization reinjection technique, QCLs can generate all-optical square-waves. Eventually, it is possible to trigger optical extreme events in QCLs with tilted optical feedback. All these experimental results allow a better understanding of the non-linear dynamics of QCLs and will extend the potential applications of this kind of semiconductor lasers.

Download or read book High Power High Beam Quality Mid infrared Quantum Cascade Lasers written by Jae Ha Ryu and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Coherent power scaling of quantum cascade lasers (QCLs) for high-power, single-mode continuous-wave (CW) operation has proven to be quite a difficult task - while the device volume could be scaled for higher output power, many other factors such as beam quality and thermal resistance are negatively impacted if the device design is not carefully considered. The main objective of this work has been to develop methods for realizing high continuous-wave (CW) output power QCLs with high beam quality and minimal beam steering. One attractive approach for tackling this problem is the use of resonant leaky-wave-coupled antiguided phase-locked laser arrays. This dissertation focusses on two approaches to achieve high coherent power: 1) one alternate to the resonant leaky-wave-coupled antiguided phase-locked array concept, so called 'reverse-taper'laser; and 2) one combining grating-coupled surface-emitting lasers (GCSELs) with resonant leaky-wave-coupled antiguided phase-locked arrays, where each array element is coupled in both the lateral and longitudinal direction; thus, has a potential for multi-watt -CW surface-emitted output powers with good beam quality and narrow spectral linewidth. The novel geometry reverse-taper QCL device can scale the output power while maintaining good beam quality and beam stability - the tapered region scales the output power, while the emitting facet is located at the narrow-end taper section, which provides mode filtering by suppressing high-order spatial modes. A small degree of collimated-beam centroid movement (

Download or read book Broadly Tunable Terahertz Difference Frequency Generation in Mid infrared Quantum Cascade Lasers written by Yifan Jiang (Ph. D. in electrical and computer engineering) and published by . This book was released on 2017 with total page 204 pages. Available in PDF, EPUB and Kindle. Book excerpt: Room-temperature terahertz (THz) sources analogous to diode lasers in the near-infrared/visible or quantum cascade lasers (QCL) in the mid-infrared (mid-IR), i.e., electrically pumped, compact, widely tunable, and suitable for low-cost production, are highly desired for feasible and inexpensive THz systems. This dissertation focuses on demonstrating broadly tunable, room-temperature THz systems based on intra-cavity difference frequency generation (DFG) in mid-IR QCLs with improved spectral capability for versatile applications. Spectral control using an external cavity provides the widest tuning range and is favored for real-world applications. DFG-THz could be spectrally tuned by either tuning one mid-IR pump or by tuning both mid-IR pumps together. I built a Littrow-type, external cavity THz DFG-QCL system that generated spectral tunable THz radiation by fixing one mid-IR pump frequency with an integrated DFB grating on top of the QCL structure and tuning the other mid-IR pump frequency with an external grating, thus demonstrating record broadband narrow linewidth THz frequency tuning from 1.2 to 5.9 THz. A Cherenkov waveguide is used in this system to extract THz radiation through the semi-insulating InP substrate; however, InP has dispersion in 1–6 THz, resulting in steering far field profiles for different THz frequencies. Replacing the InP substrate with high-resistance silicon through an adhesive bonding process solved the beam steering problem of this THz DFG-QCL system. I also built a double-Littrow, external cavity DFG-THz system that tunes both mid-IR pump frequencies using two external diffraction gratings. Such a system allows performing a comprehensive spectroscopic study of the optical nonlinearity and its dependence on the mid-infrared pump frequencies. Our work shows that the terahertz generation efficiency can vary by a factor of two or more, depending on the spectral position of the mid-infrared pumps, even for a fixed THz difference frequency. Using this system, we investigated different active region designs: bound-to-continuum, continuum-to-continuum, three-phonon-resonance, and dual-upper-state active region design. Our studies show THz DFG-QCL based a bound-to-continuum active region with gain centered around 15 μm has an order of magnitude enhancement of mid-IR to THz conversion efficiency, which provides a trend for future improvement of the power performance of THz DFG-QCLs

Download or read book Broadly Tunable Mid infrared Quantum Cascade Lasers for Spectroscopic Applications written by and published by . This book was released on with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Quantum cascade lasers are unipolar semiconductor lasers based on intersubband transitions in heterostructures. These lasers, which have demonstrated continuous wave operation at room temperature in the mid-infrared spectral range, are well suited for the realization of compact, ultra-sensitive, trace-gas sensors based on absorption spectroscopy. Up to now, only distributed feedback (DFB) single-mode devices have been used for such applications. DFB quantum cascade lasers have proven to be effective for gas sensing, but their relatively narrow tuning range, smaller or equal to about 1% of the wavelength, makes them not very versatile and limits their usefulness for spectroscopic investigations. In this thesis we developed broadly tunable external cavity quantum cascade lasers. The main advantage of these sources compared with DFBs is their broader tuning range, which is limited only by the spectral bandwidth of the gain element. We particularly studied broad gain bandwidth active regions based on bound-to-continuum designs. With that kind of active region, we have demonstrated a tuning range equal to 15% of the center wavelength at l ~ 10 mm, which was three times broader than the best values reported in the literature at that time, as well as good performance in pulsed mode at room temperature. Using a strain-compensated bound-to-continuum design emitting near 5.2 mm, we have demonstrated for the first time continuous-wave operation of an external cavity quantum cascade laser on a thermoelectric cooler. The tuning range was comparable to that of pulsed devices, but with a much better side-mode suppression ratio and a much narrower linewidth. This continuous-wave device has successfully been applied to the spectroscopy of nitric oxide in collaboration with Prof. Tittel's Laser Science Group at Rice University. High resolution absorption spectra of that gas could be acquired over a large wavelength range. We also studied heterogeneous cascade structures, that is quan.

Download or read book High Power and Efficient Mid infrared Emitting Quantum Cascade Lasers written by Suraj Suri and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Broadly Tunable Mid infrared Quantum Cascade Lasers for Spectroscopic Applications written by Richard Maulini and published by . This book was released on 2006 with total page 133 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book High power and Narrow linewidth Optimizations of Mid infrared Quantum Cascade Lasers written by Ilia Sergachev and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book High Efficiency and High Power Mid Wave Infrared Cascade Lasers written by and published by . This book was released on 2009 with total page 65 pages. Available in PDF, EPUB and Kindle. Book excerpt: Quantum cascade laser (QCL) performance continues to improve towards the requirements of applications such as infrared counter measures. However, key metrics, such as wall-plug efficiency (WPE), are still not fully met. DARPA's EMIL program continues to support progress in QCLs, and this report summarizes the Princeton team's work during Phase I of this program. Although the work systematically addressed all major facets of efficiency, the greatest advancements involved injection designs, which improved almost all efficiency components. Strain compensated QCLs with heterogeneous injectors produced low voltage defect. The active core consisted of interdigitated undoped and doped injectors followed by nominally identical optical transitions. The undoped injectors were designed with reduced voltage defect while the doped injector designs were more conventional. The measured average voltage defect was less than 79 meV. At 80 K, a 2.3 mm long, back facet high reflectance coated laser had an emission wavelength of 4.7 micrometers and output 2.3 W pulsed power with 19% peak WPE. Other QCLs emitting at 4.2 micrometers featured a low voltage defect and short injector with only four quantum wells. Devices with a voltage defect of 20 meV and a record voltage efficiency of 91% were demonstrated for pulsed operation at 180 K. Voltage efficiencies of greater than 80% were exhibited at room temperature. WPEs ranging from 21% at cryogenic temperatures to 5.3% at room temperature were achieved. Interface roughness effects were analyzed as in homogeneous broadening, explaining the temperature dependent QCL gain spectra and suggesting improved designs. Specifically, density-matrix theory revealed benefits from stronger coupling between injector and upper laser level that led to low-temperature pulsed QCLs nearing 50% WPE.

Download or read book 2 d Coherent Power Scaling of Mid infrared Quantum Cascade Lasers written by Christopher Andrew Sigler and published by . This book was released on 2018 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Scaling the continuous-wave (CW) power of quantum cascade lasers (QCLs) beyond ~5 W has proven difficult, and beam-quality degradation is common when scaling the device volume for high power. The primary objective of this work was to develop methods for spatially-coherent power scaling of mid-infrared-emitting QCLs to high CW powers. Two approaches were investigated: 1) resonant leaky-wave-coupled antiguided phase-locked laser arrays; and 2) grating-coupled surface-emitting lasers (GCSELs). These two approaches can be combined to realize high surface-emitted powers in a spatially and temporally coherent beam pattern. Optical and thermal models of planarized leaky-wave-coupled phase-locked QCL arrays were coupled together to investigate the influence of thermal lensing on modal behavior. Self-focusing under thermally-induced index variations across the array were found to impact the field profile and promote multi-moding due to gain spatial hole burning. Two techniques were found to mitigate this effect: 1) employing anti-resonant reflective-optical waveguide terminations outside the array; and 2) chirping the element width across the array to obtain identical optically-equivalent widths under CW operation, eliminating thermal lensing at a particular operating condition. Five-element phase-locked arrays of 4.7 μm-emitting QCLs were demonstrated which operate in a near-diffraction-limited beam (primarily in the in-phase array mode) to 5.1 W peak pulsed power, in agreement with simulations. Spectrally resolved near- and far-field measurements indicate that the wide spectral bandwidth of the QCL core promotes multi-mode operation at high drive levels. An optimized array design was identified to allow sole in-phase mode operation to high drive levels above threshold, indicating that full spatial coherence to high output powers does not require full temporal coherence for phase-locked laser arrays. Lastly, a novel method for obtaining a single-lobed beam pattern from transverse magnetic (TM)-polarized GCSELs is proposed: resonant coupling of the optical mode of a QCL to the antisymmetric surface plasmon mode of a 2nd-order distributed feedback metal/semiconductor grating results in strong antisymmetric-mode absorption. Lasing in the symmetric mode, resulting in a single-lobed far-field beam pattern from the substrate emission, is strongly favored around resonance. For infinite-length devices, the symmetric mode has negligible absorption loss while still being efficiently outcoupled by the grating.

Download or read book Terahertz THz Mid Infrared MIR and Near Infrared NIR Technologies for Protection of Critical Infrastructures Against Explosives and CBRN written by Mauro Fernandes Pereira and published by Springer Nature. This book was released on 2021-04-30 with total page 290 pages. Available in PDF, EPUB and Kindle. Book excerpt: Critical infrastructures are targets for terrorism and deliver a valuable vector through which the proliferation of CBRN and explosive precursors can be detected. Recent technological breakthroughs, notably in the field of near infrared (NIR), mid infrared (MIR), Terahertz (THz) and Gigahertz (GHz) sources and detectors, have led to rugged commercial devices, capable of standoff sensing a range of these dangerous substances. However, at the same time criminal and terrorist organizations have also benefited from the availability of technologies to increase the threat they pose to the security of citizens and a concerted effort is needed to improve early detection measures to identify activities, such as the production of homemade explosives or CBRN that can be potentially dangerous to society. The key global technological bottleneck to be overcome is the current lack of integration and networking of mature detection technology into early warning systems for critical infrastructures. Thus, this book brings together complementary information connecting the research of leading teams working on critical Infrastructure protection with academic developers and industrial producers of state of the art sensors.

Download or read book Quantum Cascade Lasers written by Jérôme Faist and published by Oxford University Press. This book was released on 2013-03-14 with total page 321 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book describes the physics, fabrication technology, and applications of the quantum cascade laser.

Download or read book High Performance Mid infrared emitting Quantum Cascade Lasers written by Jeremy Daniel Kirch and published by . This book was released on 2017 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The active region of conventional Quantum Cascade Lasers (QCLs) is composed of quantum wells and barriers of fixed alloy composition. As a consequence, they suffer severe carrier leakage from the upper laser level, as evidenced by low characteristic-temperature values for both the threshold current density and the slope efficiency, over a wide range of heatsink temperatures above room temperature. Here, we describe three methods by which the performance of these devices can be substantially increased. First, to suppress carrier leakage, the energy separation between the upper laser level and the next-higher energy state in the active region, E54 (or E43), needs to be increased; to this end, we propose 4.8μm-emitting, step-tapered active-region (STA) QCLs for nearly complete suppression of carrier leakage. Secondly, we introduce an 8-9μm-emitting STA-QCL design, which also employs a miniband-like carrier extraction scheme to ensures rapid depopulation of the lower laser level. We call the fast, carrier-extraction scheme resonant extraction (RE) since it involves resonant-(tunneling)-extraction not only from lower active-region levels but also from the lower laser level. When both the STA concept and miniband-like carrier extraction scheme are applied, in so-called STA-RE QCLs, it is shown that record-high internal differential efficiency hid values of ~ 86% can be achieved, by comparison to the prior state-of-the-art values of 57 to 67%. Furthermore, the fundamental upper limit for hid is shown be ~ 90%. With this improvement to internal differential efficiency, the wall-plug efficiency, hwp of mid-infrared-emitting QCLs should be ~34% higher than previously predicted, with hwp reaching values in excess of 40% for 4.6μm-emitting QCLs. Preliminary results from 5.0μm-emitting STA-RE QCLs are shown. Lastly, we show how single QCL emitters can be monolithically beam-combined to create High-Index-Contrast Photonic-Crystal (HC-PC) lasers as a means to coherently scale a QCL's output power while maintaining high beam quality, even under continuous-wave (CW) operating conditions. We present one such structure, which provided an output power of 5.5 W in a far-field beam pattern with lobewidths ~1.65 times the diffraction limit, and 82% energy contained in the central lobe. Methods to further improve on this result are also discussed.